Spark plug



A. TH IES SPARK PLUG March 16, 1954 Filed Feb. 2l, 1951 v @MW-mw? Patented Mar. 16, 1954 reo s mies LATEN T 0F FICE .SPARK PLUG .,'Adlf Thies, .Nienburg (Weser), .Germany lApplication February 21, 1951,'Serial'No;212,003

Asis known, the `interference caused by the sparkz plug is reduced and screened by the use -of .metalsleeves'or by inserting resistors in vthe ignitionline. `:Itfhas :also been suggested that :resistors belouiltV inthe spark plugs themselves, so that they form a part of the center electrode.

ADue to the 'hi-gh ignition voltagafor example, 151.000 volta-'resistors of high resistance, must gpossess a certain `minimum volume. 'Due to this volume it is impossible to install suchfresistors 'in .sparkplugs of known design.

In connection with the resistors which are installed in the spark plugs and forma fixed part of thecenter electrode, i. e., are-rigidly .connected with the other structural' parts, they must `*with- :s-tand -all impacts occurring during operation,

such as these which spark plugs are normally subjected to as, for example, when used in motor vehicles. .'Inasmuch .as the-material of theresistors is always susceptible -toA impact, .disturbiances in the ignition and even breakdowns of 1theresistors-are unavoidable if they .are rigidly c.installed-,as in. the known designs. Similarly,` the ,installationof the resistorsrin these conventional sparkplugs. causes considerable diiiculties L inas- -much .asadependable arcless .contact vbetween :theends of theresistor and the. center electrode or theignition cable must be assured.

Oneobject ofthis invention is a-sparkgpl-ug withan.. interference eliminator ywhich is not Isubject to the. .aforementioned dinculties. -fandfurtherobjects will become apparent from .the following description read in Vconjunction with` the .drawing in which:

rFig.v 1 isa partial sectional view `of aspark plug with an interference eliminator :according to the invention; and g jlig. 2 isa .partial sectionof part of Aa spark ,plug according to the present invention with :a ...special .design of the .contactfmember support.

It has now been found that for an eiTecti-ve y:sistance-of at -least 10,000 ohms are required.

.This Ahigh resistance willattenuate oscillations .voila :verycghigh-LLfrequency, iaszior example; Ithe 'rms .v9 Claims. (Cl. 315-58) 2 iieldzof meter and fdecimeterwaves, whichrherevtoforekncwn expedients `would not effectively eliminate. The spark plug according tothe iinvention has :an interference reliminator which avoids the-disadvantages of theknov/n interference `relirninators, and fwill vnot :interfere vwith the reception of radio or `television sets, even those located in vthe :immediate vicinity, land' has further considerable advantages both in operation vand manufacture.

The sparkl plug; according to the invention; lis provided with a resistance 'member Vwhich in contrast to the known linterference eliminators,

Ydoes'not form a Xed-partof the centerzelectrode,

and is :not rigidly attached`- thereto, :but is elas- `tically arranged :between the yinner endfof-the rcenter electrode (which 'lisssurrounded :by an insulating jacket), andfa contact member for conmeeting-'the ignition;cablethereto.

:By mounting :the resistance wmember in 'the elastic support, it :is no' longer subjected to im- ;pact stresses during operationcrsubi'ected'to any type of mechanical strain. In addition to `this, expansion of Aall linner Astructural members of the spark plug lying ibetween-thespark gap land the cable connection is allowed,- so that'allstresses :of the material `which Aoccur due -to ,the 4nnusually large temperature variations 4encounter-ed in .the operation ,of the spark-plug are 'considerably reduced. In .addition to ithis, 'complete -arcless contact fromthe..center electrode-t0 the .ignition cable isachieved.

In 'accordancewwith a y'preferred embodiment iof the invention. the contact member is developed as aibushing for the end ofthe :ignition cable,

which of lcoursexvvillralsov allow the insertion. of an 'ignition `cable end: provided Awith Ya suitable plug.

The--contact'member is held according toxth'e invention 1by a which iis 'fastened to-.the inner wall ofan insulating'member preferably developed in the form of a hollowfcylinderfand introduced into `thel metallic sparkv plug shell.

In .order toxobtain anfelastic-support of the-resistancey member, the --contact 'member` is rslidably vsupportedfiin .the :ring and `a spring is 'arranged ther .resistance member, :a :compression Yfspring is yused. 'If the thrust surface is on the opposite side, `tl'lenwartension'spring fastened at its ends tothe ring and contact member is used. inasmuch as the 'ring isl positioned ata,v distancel froml the parts `of the spark plug 'which' become excessively' hot during operation'andfis not subjected tof'substantial thermal stresses, insulating plastics such as vulkanflber may be readily used as the construction material for the ring.

It is preferable, however, to construct the ring of metal or to provide it with a conductive coating for if the ring is made in this manner a condenser consisting of the ring, insulating material, and the metallic spark plug shell is formed, and the metallic spark plug shell and the ring acting as the plates and the insulating member acting as the dielectric. The condenser action of these three elements will considerably increase the capacitance between the ignition cable and the ground. As is already known, the loss of ignition power caused by inserting a resistance in the ignition line can be eliminated by increasing the capacitance between the center electrode and the ground which is done in conventional practice by inserting condensers in parallel.

The capacitance may be still further increased a substantial amount by inserting a metallic sleeve, wider than the ring between the ring and the inner wall of the insulating member.

It is also possible to provide the inner wall of the insulating member with a conductive coating as, for example, metallizing it, which is in electric contact with the ring.

If the ring is produced of a flexible metal as, for example, copper, the fastening within the insulating member may be advantageously eiected by subjecting the metal to pressure upon both sides.

In accordance with the present invention construction is possible which will allow the removal and replacement of the contact member Vand in particular the resistance member at any time. According to this construction the ring may be formed in two parts and consist of a slit nut provided with an internal cone and a conical screw threaded to lit into the internal cone of the slit nut `and provided with a bore for the contact member. Upon screwing in the screw, which is preferably provided with a recess or projection for engagement by a tool, the nut is spread and a firm seat within the insulating member is obtained. The screw may be unscrewed in an eX- tremely simple manner and the individual parts, such as, for example, the resistance member, can be replaced.

The resistance member is advantageously displaceably supported by means of insulating rings on the inner wall of the insulating member, so that a concentric support of the resistance member within the insulating member is assured.

In accordance with a further preferred embodiment of the invention the metallic spark plug shell, and advisedly the insulating member, extend beyond the place of support of the contact member, so that the spark plug shell itself serves as a screen for the high frequency oscillations and removes any necessity for arranging special screening sleeves on the spark plug body. In this manner there is furthermore obtained sunicient room to hold the resistance members having a high resistance, for example, 10,000 ohms and more within the insulating member. In this construction it is possible to install commercial resistance members without making any change whatsoever.

The resistance members may be constructed of the materials conventionally known and used for resistances and need only be formed in a shape to t within the plug.

Referring to the drawings the cylindrical metal spark plug shell I is, as customary, provided with Athe thread 2 for screwing into the motor housing or cylinder head, the ground electrode 3 and the hexagon 4. The center electrode 6 surrounded by insulating jacket 5 is hermetically fastened to the inner wall of spark plug shell I by means of the forced in metal ring 1.

In accordance with the invention, the resistance element 8 is elastically supported between the contact member I0 and the center electrode t, provided with nut 9. The contact member I0 is developed as a bushing for the introduction of the ignition cable end or a plug arranged on the ignition cable end` Ring I I which is attached to the inner shell of the hollow cylindrical insulating member serves to support contact member I0.

In order to obtain the elastic support of resistance member 8, contact member I0 is displaceably supported in ring I I and a compression spring I4 is provided between ring I I and thrust surface I3 provided on contact member I8.

Ring II preferably consists of metal, for example copper, and is force-fitted within insulating member I2. In this manner, ring l I, together with spark plug shell I and insulating member l2 as dielectric, forms a condenser by which the capacitance between the ignition cable and the ground is considerably increased. A further increase cf the capacitance is obtained by the fact that the metal sleeve I5 which is wider than ring II, is arranged between ring Il and insulating member I2. To obtain the same effect, the inner wall of the insulating body I2 may also be partially provided, for example metallized, with a conductive coating which is in electric contact with ring I I.

Resistance member 8 is displaceably supported by means of insulating rings IB and I1, so that a concentric support within insulating member I2 is assured.

For complete high frequency screening, spark plug shell I and insulating member l2 are extended to such an extent beyond the place of support of contact member IG that special screening sleeves are not required.

In Fig. 2, there is shown an emboClimentl of the support of contact member I by means of which a particularly easy replacement of the inner parts of the spark plug, especially the resistance member 8, is made possible.

Ring II is developed in two parts and consists of the slit nut IIa provided with an inner cone and the conical screw lib provided with a bore for contact member I0. When assembling, screw IIb with the Contact member I@ displaceably arranged in its support and the compression spring I4 are rst of all screwed loosely into the slit nut IIa outside of the spark plug. Thereupon, all parts are introduced together into the insulating member I2 until contact member lil exerts spring pressure against resistance member 8. Finally, screw IIb is tightened so that the slit nut Ha is spread and assures a drm hold. In the reverse sequence of the steps indicated, the bipartite ring II can be easily removed from insulating member I2 and resistance member 8 can easily be replaced.

In order to facilitate the tightening or loosening of screw IIb by means of a tool inserted in the insulating body, recesses I8 are provided on screw IIb.

I claim:

1. In a spark plug having a hollow metallic spark plug shell with an insulated central bore and an insulated central electrode axially positioned in the center of the bore, the improvement which comprises a ring in holding contact with the surface of said insulated bore positioned above the top of said central electrode, a contact member` for the connection of ignition cable thereto axially displaceably supported in said ring, a resistance element positioned between and in direct electrical contact with the top of said central electrode and said contact element, and spring means positioned for electrically urging said Contact member toward said central electrode and thereby in direct electrical contact with said resistance element.

2. Improvement according to claim 1, in which at least the surface portion of said ring is formed with an electrically conductive material.

3. Improvement according to claim 1, in which said contact member is developed as a sleeve for receiving the end of an ignition cable.

4. Improvement according to claim 3, in which a metal sleeve is positioned between said ring and the surface of said insulated bore, said metal sleeve being wider than said ring.

5. Improvement according to claim 1, in which said ring is a bipartite ring comprising a nut portion provided with an inner cone and conical screw portion provided with a bore for the said contact member.

6. Improvement according to claim 5, in which said screw portion is provided with engagement means for a screw tool.

'7. Improvement; according to claim 1, in which said resistance element is elastically supported by at least one insulating ring.

8. Improvement according to claim 1, in which the metallic spark plug shell extends suiiiciently past said contact member to provide high frequency screening.

9. Improvement according to claim 1, in which said resistance is centrally positioned in the spark plug shell in spaced relation to the inner walls thereof, whereby said resistance is protected from thermal exposure.

ADOLF THIES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,960,317 Rabezzana May 29, 1934 2,029,570 Kasarjian Feb. 4, 1936 2,071,571 Rabezzana Feb. 23, 1937 2,081,500 Nowosielski May 25, 1937 2,129,961 RabeZZana Sept. 13, 1938 2,173,766 Ramsay Sept. 19, 1939 

